@seanf These are meaningful names, they are just shortened to save room. You can find references for them here: http://webassets-zanata.rhcloud.com/1/styleguide/

Any "Global" components will have a shortened prefix. "Normal" components will not e.g. "label", "label--highlight".

Classes with a single letter appended are global components. e.g. w = width, l = layout.
-- means it is a modifier
__ means it is a sub element

So "w--1-12" means make it one twelfth of the width (.083333333%)
or
"l--pad-v-1" means it is part of the layout component, it's giving the element padding of 1 vertical rhythm vertically (top & bottom).

I have a similar CSS styleguide to this https://github.com/csswizardry/CSS-Guidelines